Cardiopulmonary resuscitation (CPR) is a medical procedure performed on patients to maintain some level of circulatory and respiratory functions when patients otherwise have limited or no circulatory and respiratory functions. CPR is generally not a procedure that restarts circulatory and respiratory functions, but can be effective to preserve enough circulatory and respiratory functions for a patient to survive until the patient's own circulatory and respiratory functions are restored. CPR typically includes frequent chest compressions that usually are performed by pushing on or around the patient's sternum while the patient is laying on the patient's back. For example, chest compressions can be performed at a rate of about 100 compressions per minute and at a depth of about 5 cm per compression for an adult patient. The frequency and depth of compressions can vary based on the age and size of a particular patient.
Manual CPR has several disadvantages. A person performing CPR, such as a medical first-responder, must exert considerable physical effort to maintain proper compression timing and depth. Over time, fatigue can set in and compressions can become less regular and less effective. The person performing CPR must also divert mental attention to performing manual CPR properly and may not be able to focus on other tasks that could help the patient. For example, a person performing CPR at a rate of 100 compressions per minute would likely not be able to simultaneously prepare a defibrillator for use to attempt to restart the patient's heart. Mechanical compression devices can be used with CPR to perform compressions that would otherwise be done manually. Mechanical compression devices can provide advantages such as providing constant, proper compressions for sustained lengths of time without fatiguing, freeing medical personal to perform other tasks besides CPR compressions, and being usable in smaller spaces than would be required by a person performing CPR compressions.